The present invention generally relates to a digital printer and a technique for utilizing a printer, and more particularly, to a technique for realizing harmonious use of a plurality of printers which differ from one another in terms of a language interpretation capability, a network communications function, or a rendering capability, for using an underperforming printer in the same manner as a high-performance printer, or for causing a plurality of printers to complement to one another with regard to performance deficiencies.
Various languages have been developed for use in describing print commands supplied to a printer from a host computer. Of these languages, some, such as a page description language “PostScript™” of Adobe Systems Incorporated in the U.S., have a very versatile expression capability and are capable of freely expressing complicated graphics which cannot be described by any other language. So long as such a high-function, high-level language is employed, complicated graphics can be printed beautifully at high speed. To this end, the printer must have a function of being able to interpret and render the high-function language. However, a printer capable of interpreting a high-function language such as PostScript is more expensive than a printer capable of interpreting solely a lower-function language. In a case where there are used a plurality of printers connected to a communications network, e.g., a LAN, if printers compatible with a high-function language are selected for all the printers, a very high cost will be incurred at the time of introduction of the printers.
When a plurality of printers are connected to the network, the following problem will arise. More specifically, provided that a plurality of types of printers (e.g., page printers and serial printers) are connected to the network or that a plurality of printers produced by different manufacturers are connected to the network, the language that can be interpreted differs from printer to printer. For this reason, the user of the host computer is required to determine beforehand a printer which he desires to use and to select a language (in effect, a printer driver) suitable for the printer. However, so long as print quality is guaranteed, use of any printer poses no problems for the user. Accordingly, it is convenient for the user to utilize various printers under a unified method without consideration of the type of printer or printer driver.
In an existing communications network, e.g., the Internet, one terminal is usually assigned one IP address. Communication between network-compatible terminals, each of which has an IP address and a TCP/IP execution function, form the basis of the network.
For example, in a case where all the printers disposed in an office are to be connected to the Internet, there are many types of existing printers which cannot be directly connected to the Internet, and hence an expensive network adapter must be attached to each of these printers, resulting in a considerably large economic burden. Further, there are many types of existing printers incapable of operating with the network.
The foregoing problem may be expressed in terms of a more general problem: that is, a plurality of terminals including both network-incompatible terminals and network-compatible terminals are collected into one group (e.g., all the printers disposed in an office are collected into one group), and no existing means provides a relay function capable of connecting the entire group to a network.
With regard to a relay function related to the network, in an existing line there is provided a router which performs a relaying operation called a routing operation (e.g., selection of a communications path, data exchange between adjacent networks, and management of IP addresses of the network) for routing data transferred over the Internet to a desired terminal. However, since the router is intended to relay data between domains within the Internet, the router cannot serve as means for solving the problem, i.e., means for connecting to a network a group including network-incompatible terminals such as those mentioned previously.
A document—which is supplied via WWW service over the Internet and which is written in, e.g., HTML,—is a composite document comprising text characters and another type of resource, such as audio, a dynamic image, or a static image, embedded into the text characters. A plurality of types of resources are incorporated into such a composite document in their respective unique file formats. For example, a character file is incorporated in a text format, a HTML format, or a file format unique to an application used for preparing the file: a static image is incorporated into a composite document in a JPEG or GIF format; and a dynamic image is incorporated into a composite document in an MPEG format.
An existing printer is provided with a mere renderer (i.e., a module for performing a rendering operation or preparing a print image of a document) corresponding to a certain printer control language. In an existing print system comprising an existing printer connected to a host computer, when a composite document such as that mentioned previously is printed, the host computer interprets the file format of each resource contained in the composite document. The host computer converts document data into data expressed in a specific printer control language understandable to the printer and transfers the thus-converted print data to the printer. The printer interprets the data expressed in the specific printer control language and prepares and prints a print image of the document.
As mentioned above, an existing printer can understand only data expressed in a specific printer control language. In a case where data regarding a composite document are printed, the host computer must interpret various file formats contained in a composite document and convert the file formats into data described in the printer control language. However, in the case of a network-compatible printer capable of being connected to a network such as the Internet, the printer has the function of following a network communications protocol such as TCP/IP. Accordingly, if the printer can interpret and print a composite document capable of being transferred according to the communications protocol, great convenience is afforded to the user.